The effect of oral methadone on the QTc interval in cancer pain patients.

Introduction: The QTc prolongation effect of methadone has been extensively studied at higher doses commonly used in opioid dependence maintenance therapy, but evidence remains limited regarding its impact at the lower doses typically prescribed for cancer pain. This study aims to evaluate the effect of oral methadone on QTc intervals in cancer pain patients.

Methods: A retrospective analysis was performed on adult patients initiated on oral methadone therapy for cancer. Pre- and post-methadone QTc intervals, obtained within six months before and between six to twelve months after methadone initiation, respectively, were compared. The proportion of patients with QTc intervals greater than 450 msec and 500 msec before and after methadone therapy were compared.

Results: Among the total of 310 patients, the mean pre-methadone QTc was 384.5 ± 37.8 msec (95% CI 380.3, 388.7) and the mean post-methadone QTc was 388.5 ± 43.4 msec (95% CI 383.6, 393.3). No statistically significant difference in QTc interval was observed (p = 0.1). The proportion of patients with a QTc greater than 450 msec and 500 msec pre- and post-methadone were also not statistically different.

Conclusion: Lower doses of oral methadone for cancer pain do not result in significant QTc prolongation.